1. Field of the Invention
This invention relates to a stove for cooking food and like appliances with a door having a window and a temperature indicating device thereon.
2. Background Information
In general terms, a stove for cooking food comprises a stove body, with the stove body being configured with a base and the stove body further being configured with an interior chamber confined by walls comprising side walls, a front wall, and a rear wall.
An oven is disposed in the interior chamber of the stove body and the oven comprising a heating arrangement configured and disposed to provide heating to cook food in the oven. There is further provided control apparatus to control said the heating arrangement.
The oven usually comprises a door in the front wall, which door may comprise a window arrangement, with the window arrangement comprising a viewing area to view the interior of the oven.
U. S. Pat. No. 5,432,321 issued to Gerl on Jul. 11, 1995 discloses an oven which includes a normal heating device, a partial heating capacity device, a first indicator device associated with the normal heating device, a second indicator device associated with the partial heating capacity device, and a control unit. The control unit turns on a full heating capacity of the normal heating device in a preheating phase and turns on the first indicator device to indicate that the normal heating device is on. The control unit turns on the partial heating capacity device in the preheating phase and turns on the second indicator device to indicate the preheating phase. The control unit automatically switches over the normal heating device to a reduced heating capacity in a continued heating phase, when a selected command temperature is reached. The control unit turns off the partial heating capacity device and automatically turns off the second indicator device simultaneously with the switchover to the continued heating phase.
U.S. Pat. No. 5,928,540 issued to Antoine et al. on Jul. 27, 1999 refers to an oven door for closing a cooking chamber of an oven, the door being composed of: a frame on the oven; an inner wall and an outer wall both supported by the frame so that the inner wall is located between the cooking chamber and the outer wall, the inner wall and outer wall being positioned relative to one another to delimit an air space; and ventilation elements for establishing a flow of air between the inner wall and the outer wall in order to maintain the outer wall at a low temperature during a cooking operation, wherein the inner wall is made of glass, and the outer wall is removable from the frame and is made of a plastic material selected to withstand the temperatures to which it will be exposed during any cooking operation.
The window arrangement referred to above may comprise a plurality of panes, for example, a first pane and a second pane, with the second pane being disposed adjacent the first pane, and the first pane being disposed to face towards the interior of the oven upon installation in the stove.
The second pane would be disposed to face towards the exterior of the stove upon installation in the stove.
It would be advantageous, for example, for cleaning the oven to determine the interior temperature of the oven.
A temperature indicating device of the prior art is described in Federal Republic of Germany Published Patent Application No. DOS 19836732 A1 published on Feb. 24, 2000. A temperature-sensing element is attached in the vicinity of the surface of the door and, as the temperature of the door rises, indicates the elevated door temperature by changing color. One essential feature of this device is that it does not indicate the temperature of the interior of the oven, but only the temperature of the door. The element is preferably a film that is attached to the inside of the door and contains chemical substances that visibly change color as the temperature changes. Accordingly, the element must be designed so that it can survive the high temperatures to which it is exposed in ovens. A temperature-sensing element of this type is complex and expensive to manufacture.
U.S. Pat. No. 5,499,597 issued to Kronberg on Mar. 19, 1996 and entitled, xe2x80x9cOptical temperature indicator using thermochromic semiconductors,xe2x80x9d describes thermochromic materials to indicate temperatures, which can be used to indicate hazardous temperatures on hotplates.
In the prior art, bimetallic or electronic sensors are used as the temperature sensors to indicate the temperature of the interior of an oven. These sensors act on a display by means of a corresponding electronic system. Circuits of this type, are complex and expensive to manufacture. They also require power to operate.
International Published Application WO 97/26486 published on July 1997, entitled, xe2x80x9cA control device for a domestic ovenxe2x80x9d; and International Published Application WO 97/34490 published on Sep. 25, 1997, entitled, xe2x80x9cA heater unit for ovens,xe2x80x9d describe various requirements for temperature indicators on the door of a domestic oven.
Austrian Patent No. 202,660 of Sep. 15, 1958 describes a roaster for electric ovens with a thermostatic control that is attached to the door. The controller is located between two shells of the door. A thermally conducting body transmits the heat from the inner shell of the door to a bimetallic switch. There is an indicator light that shows the status of the switch.
U.S. Pat. No. 5,589,958 issued to Lieb on Dec. 31, 1996 and entitled, xe2x80x9cKitchen ensemble having windows with controllable opacity,xe2x80x9d describes a kitchen arrangement on which the front windows can be switched into a transparent or opaque status.
East German Patent No. DD 234 298 A 1 is for an adhesive film that indicates the temperature. This film is used to indicate the temperature in electric household appliances.
Japanese Published Patent Application JP 11351729 A, corresponding to U.S. Pat. No. 5,996,357 issued to Park on Dec. 7, 1999 and entitled, xe2x80x9cSystem for checking an internal temperature of a refrigerator by using a thermochromic member,xe2x80x9d describes a device to indicate the interior temperature of a cooling unit. For this purpose, the device has a thermochromic element.
The object of the invention is to provide a stove and like appliance having a window with an indicator device that indicates when a specified temperature range in the interior of a heating and/or cooling device has been reached by changing color, whereby in a heating device, the temperature indicator device is not damaged by the high temperatures inside the oven.
The invention teaches that this object can be achieved by a stove for cooking food, said stove comprising: a stove body; said stove body being configured with a base; said stove body being configured with an interior confined by walls comprising side walls, a front wall, and a rear wall; an oven disposed in said interior of stove body; said oven comprising a heating arrangement configured and disposed to provide heating to cook food in said oven; control apparatus to control said heating arrangement; said oven comprising a door in said front wall; said door comprising a window arrangement, said window arrangement comprising a viewing area to view the interior of said oven; said window arrangement comprising a first pane and a second pane; said second pane being disposed adjacent said first pane; said first pane being disposed to face towards said interior of said oven upon installation in said stove; said second pane being disposed to face towards the exterior of said stove upon installation in said stove; and an indicator disposed adjacent to or in said second pane; said indicator being configured to change color upon the interior temperature of said oven reaching a predetermined temperature.
The invention teaches that this object can be accomplished, in accordance with one aspect, on a temperature indicator device of the type described above by the features comprising, in accordance with one aspect of the invention, that between two plates of the glass door that consists of two or more plates there is a thermochromic coating, whereby the thermochromic coating is designed and located so that it changes color when the interior temperature of the heating and/or cooling device is from approximately minus twenty-five degrees Celsius (minus thirteen degrees Fahrenheit) to plus one hundred and twenty degrees Celsius (plus two hundred and forty-eight degrees Fahrenheit).
Because the thermochromic coating is provided between two plates of the glass door, it is exposed only indirectly to the temperature of the interior of the oven. It is not exposed to the maximum temperature of the interior of the oven. Therefore, as the thermochromic coating, an economical and thermosensitive color coating can be used that can be attached to the plate in question using the screen printing process or is in the form of a film, preferably a polymer film. The temperature indicator device is therefore significantly more economical than a corresponding electronic temperature display device.
The thermochromic coating does not indicate the door temperature, but the temperature of the interior of the oven. Glass doors consisting of two or more plates are designed so that their outside temperature does not present any hazards to users. Therefore it is not necessary to warn the user about the high temperature of the door.
The location in which the thermochromic coating is applied is preferably selected so that at the maximum temperature of the interior of the oven, which is approximately two hundred and eighty degrees Celsius (five hundred and thirty-six degrees Fahrenheit) to three hundred degrees Celsius (five hundred and seventy-two degrees Fahrenheit), the temperature on the coating does not exceed one hundred and twenty degrees Celsius (two hundred and forty-eight degrees Fahrenheit). Thermosensitive paints that are not damaged at temperatures up to one hundred and twenty degrees Celsius (two hundred and forty-eight degrees Fahrenheit) are available commercially.
In one preferred development of the invention, the thermochromic coating is applied to the inside of the outermost plate of the glass door.
During the operation of the domestic oven, deposits or encrustations or incrustations are formed in the interior. To remove these deposits, the prior art discloses a cleaning process. During this cleaning process, a cleaning fluid is introduced into the interior of the oven, where it evaporates and dissolves the encrustations. The optimum cleaning results can be achieved if the cleaning fluid is introduced when the interior of the oven is at a temperature of approximately forty degrees Celsius (one hundred and four degrees Fahrenheit). The temperature indicator device described above is particularly well suited for making this temperature visible in the form of a change in the color of the thermochromic coating.
The temperature indicator device described above can also be used in other ovens to indicate a characteristic interior temperature or the instantaneous interior temperature. One example of the use of an indicator device as taught by the invention is the indication of residual heat. In this case, residual heat is defined as the heat that remains inside the oven after the oven has been turned off.
Thus, there is provided, in accordance with one aspect of the present invention, a temperature indicating device on a glass door of a heating and/or cooling device, whereby an externally visible color change indicates the temperature.
Additional advantageous developments of the invention are illustrated in the accompanying drawings and the related portions of the description, as well as in the dependent claims.
When the word xe2x80x9cinventionxe2x80x9d is used in this specification, the word xe2x80x9cinventionxe2x80x9d includes xe2x80x9cinventionsxe2x80x9d, that is the plural of xe2x80x9cinventionxe2x80x9d. By stating xe2x80x9cinventionxe2x80x9d, the Applicants do not in any way admit that the present application does not include more than one patentably and non-obviously distinct invention, and maintain that this application may include more than one patentably and non-obviously distinct invention. The Applicants hereby assert that the disclosure of this application may include more than one invention, and, in the event that there is more than one invention, that these inventions may be patentable and non-obvious one with respect to the other.